Means for stopping electromotors.



No. 668,030. 4 I Patanted Feb. 12,4901.

' .1. J. woon.

MEANS FOR STOPPING ELECTROIIOTOBS.

(Aypliution filed Oct. I5, 1900.)

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INVENTOR:-

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No. 668,030. Patented Fab. l2, |9o|.

J. J. moo IEANS FOR STOPPIIG'ELECTROIOTOIS.

(Applimtinn me Oct. 15, 1900. (lo 'lodol.)

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s INVENTOR:

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WITNESSES:

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UNITED STATES PATENT OFFICE.

JAMES J. WOOD, OF FORT WAYNE, INDIANA.

MEANS FOR STOPPING ELECTROMOTORS.

SPECIFICATION forming part of Letters Patent N0. dated- F r ary 1901-Application filed October 15, 1900. Serial No, 33,040. No model.)

To a, whom it may concern.-

Be it known that I, JAMES J. WOOD, a citizen of the United States,residing at Fort Wayne, in the county of Allen and State of Indiana,have invented certain new and useful Improvements in Means for StoppingElectromotors, of which the following is a specification.

This invention provides an improved controlling means for electromotorsadapted to break the circuit and stop the motor in the case either of acessation of current or of an overload of the motor.

It has been customary in starting and stopping devices for electromotorsto employ a circuit-breaker or switch controlled by two electromagneticdevices, the one responding to an overload or maximum current and theother responding to a minimum current or cessation of current, thesemagnets being so connected to the circuit-breaker or switch as to breakthe circuit to the motor in the event of either an overload or anextreme diminution or cessation of electric energy. It has been proposedto simplify such mechanisms by providing a single magnet to perform thefunctions of both the overload and so-called underload magnets. Suchcombined overload and underload magnet has had a single winding ofcoarse Wire connected in series with the motor and has been constructedto release the circuit-breaking means upon its magnetization ceasing orfalling to a minimum, as in the case of a break in the circuit, orrising to a maximum, as in the case of an overload. Such a means forprotecting the electromotor is operative under certain conditions, butis subject to the disadvantage that it is liable to act too quickly andis not adapted to a motor operating with an accelerating load. Forexample, it has been found that under some circumstances the mereswitching over from one dynamo to another at the generating-station willcause such a control-magnet to act to cut the motor out of circuit, or,if the motor is operating with an acceleratin g load, like an electricelevator, such acceleration will so nearly extinguish the on rrentthrough the exciting-coil of the magnet as to cause the magnet to cutout the motor.

The object of my present invention is to overcome these disadvantagesand enable a combined overload and underload magnet to be used for theprotection of an electromotor under all the circumstances occuring inpractice. To these ends,according to my invention I provide acontrolling-magnet with two windings, Wound to receive currents in likedirection, so as to cooperate in magnetizing the magnet, one being aseries coil connected in series with the motor-armature and the otherbeing a shunt-coil connected in series with the field-exciting coil of amotor. Hence whenever a current is flowing to or from thearmature-terminals of the motor the control magnet is proportionatelymagnetized by the series coil, and whenever a current traverses thefield-coil of the motor to maintain its field excitation thecontrol-magnet is proportionately excited by means of its shunt-winding.If the main circuit is broken,the electromotor continuing to run underits momentum mainrains for a short time its own excitation, and

during such time the control-magnet is proportionately excited, so thatits action as an underload-magnet is retarded. If the motor races underan accelerating load, its counter electromotive force, whichmayextinguish the current in the series coil of the control-magnet,augments the current through the shuntcoil thereof, so that it maintainsthe magnetization of the contro1-magnet.

My invention also provides a novel construction of control-magnetadapted to respond to either a maximum or minimum magnetization.

My invention is ordinarily and preferably applied in connection with amotor-starting box or rheostat wherein the movement of a rheostatarmafter the circuit is closed to start the motor successively cuts outresistances which are in series with the armature, so that when thelatter reaches full speed it may be connected directly in the externalcircuit without interposed resistance. I prefer to apply my invention tosuch a resistance-box in which the rheostat-arrn is impelled by a springto the position of maximum resistance and is held against thespring-pressure in the position of no resistance by the control-magnet,which is constructed as a detent, whereby when the control-magnetbecomes over or under magnetized it releases the arm, which, moving overunder the tension of its spring,

first introduces the resistances in circuit and then actuates thecircuit-ln'eaker to break the main circuit. I here show and describeonly so much of such construction as is necessary to enable thepreferred application of my present invention to be understood.

Figure 1 of the accompanying drawings is a diagrammatic view showing thecircuit connections and windings, the parts being shown in the positionof normal running of the motor. Fig. 2 is an elevation showing the frontof the starting-box with the parts in position for starting the motor.Fig. 3 is a section of the control-magnet, showing the specificconstruction of the latter and its engagement with the rheostat-arm whenin the position of normal running. Figs. 4 and 5 are similar views toFig. 3, the former showing the action of the magnet in the case of anunderload or cessation of current and the latter in the case of anoverload or extreme augmentation of current. Fig. 6 is a plan of the topplate of the controlling-magnet. Fig. 7 is a fragmentary side view,looking from the left in Fig. 2, showing a means for causing therheostat-arm to operate a switch. Figs. 8 and 9 are crosssections ofmodified forms of magnets.

In order that one mode of applying my present invention may beunderstood, I will describe in some detail the motor starting andstopping means shown in the drawings, the particular means here shownbeing that set forth in my allowed application, Serial No. 723,498,filed July 11, 1899, PatentNo.663,207, granted December 4, 1900. It isunderstood, however, that my invention is not necessarily restricted inits application to the particular means shown and described.

Let A designate the base or front plate of the starting-box or rheostat,of which a a are the contact segments or terminals of theresistant-coils, and B is the contact-arm, which swings over the seriesof segments, turning around a central stud O, and formed, as usual, witha suitable handle and with a contact spring or plate I). The contact-armBis formed with a short arm B, which in normal use is engaged by thecontrolling-magnet or magnetic detent D, thereby holding the arm in theposition shown in Fig. 1, and it has another short arm B to which isconnected a suitably-stiff spring E, the opposite end of which isattached to a suitable fixed point a on the base A, the eifect of thisspring being upon the release of the contact-arm by thecontrolling-magnet D to throw the arm across the series of contacts tothe position shown in Fig. 2, and thereby cut in the resistance of theentire series of coils, which coils are indicated diagrammatically at dd in Fig. 1.

Mounted upon the plate A is a double-pole switch F, of any suitable orusual construction, which in the construction shown consists of twoconducting-bladesff, pivoted to circuit-terminals e e, to which areconnected the main-circuit wires w w, Fig. l, and the upper ends ofwhich are coupled together by an insulating-bar g, to which is attacheda handle F. \Vhen the switch is closed, as shown, the upper ends of theblades ff enter into forked contacts h h, respectively. These contactsare connected, as shown in Fig. 1, the former to a binding-post 20,which connects by a wire 21 to one terminal or brush of the motor, whilethe opposite terminal thereof connects by wire 22 to binding-post 23,which is connected by wire 24 to the terminal contact-segment a of theseries of segments a, while the opposite contact-piece 7t connects bywire 25 to the winding or coil 1' of the controlling-magnet D, theopposite terminal of this coil being connected by wire 26 to the pivot0, upon which the contact-arm 13 turns. This pivot C is also connectedby a wire 27 with the coil or winding L. of the magnet D, the oppositeend of which is led to a binding-post 28, to which post is connected theshunt-wire 29, leading to one terminal of the field-magnet coil 30 ofthe motor, the opposite terminal of which connects by wire 31 to thewire 21. The motor shown in Fig. 1 (designated as a whole by the letterM) is of the shunt-wound type.

When the doublepole knife switch F is thrown down, it of course breaksthe main circuit 20 w. For thus throwing it down antomatically I providea switchactuator,which consists of means for throwing out the switch Fclear of its contacts 71- h, which means is actuated by the contact-armB when the latterswings over under the impulse of its spring E to theposition shown in Fig. 2 and strikes a pin or buffer a. Theswitch-actuator is therefore a sort of kicker for imparting an outwardor forward thrust to the switch F upon being itself struck by the arm Bwhen the latter has traveled home. I do not illustrate the preferredform of this actuator, as it forms no necessary part of my presentinvention and is fully set forth in my aforesaid application; bnt tomake clear its essential principle I illustrate in Fig. 7 a simpleconstruction of such kicker, consisting of an elbow-lever pivoted atjand arranged to be struck at one side by the arm B when the latter fiiesover and adapted to communicate this blow in an outward direction tothrow the switch F forward.

I will now describe in detail the particular construction ofcontrolliiiig-magnet or mag netic detent D which is shown in thedrawings. This magnet is shown as of the solenoid type, its coils iand ibeing wound in any suitable manner upon a supporting tube or spoolt' Asshown, the series coil i is wound above and the shunt-coil t" is woundbelow; but I do not limit myself to this arrangement. The upper head ofthe spool is a plate '20, (shown separatelyin Fig. 6,) having at itslefthand end forked arms, between which is pivoted a catch arm or dog 11which is pressed toward the left by a spring y, housed in a socket inthe plate or head. This catch is formed with a projection or tooth 2;,engaging a tooth or plate 0) on the arm B. The upper end of thecatch-dog y is connected by a toggle-link z to a central rod ,2, towhich in turn is connected a toggle-link 2 the opposite end of which ispivoted to an arm at the right of the plate w The rod 2 passes downthrough the spool, and on its threaded lower end is attached thesolenoid-core J, constituting the movable member of the control-magnet.This core preferably screws on the rod and has a set-nut J In throwingover the rheostat-arm B to the position of normal running its arm Bcomes down and presses back the catch 3 against its spring 1 so that thecatch-plate 1) passes beneath the tooth c. To facilitate this, the teeth12 o are (one or both) beveled at their ends. Fig. 3 shows the positionof the parts in the condition of normal running, the arm 13 being heldby the catch-dog y and the solenoid-core occupyinga position mainlywithin the shuntcoil 2" and the toggle-links e" 2 being extended. Ifunder these conditions the current should increase beyond the maximumfor which the instrumentis adapted, this increased current in the seriescoilz' would draw the core J upward to the position shown in Fig. 5, sothat by communicating an upward thrust through the rod .2 it would bendthe toggle-links upward, as shown in that figure, and thereby pullbackthe dog y and free the arm B, as there shown. If, on the contrary, thecurrent should cease or fall below the minimum provided for, the weightof the core J would be no longer sustained by the attraction of thecoils and the core would fall to the position shown in Fig. 4, therebycommunicating a downward pull to the toggles and through the latterpulling the catch-dog y toward the right, as shown, and hence freeingthe arm B. These movements communicated to the toggles cause the upperend of the rod .2 to move in an arc, and hence this rod is flattened atZ3 to render it flexible.

In starting the motor the closing of the switch F causes the normalexciting-current to flow through the shunt-circuit, thereby energizingthe coil t" and drawing up the core from the position shown in Fig. t tothat. shown in Fig. 3, where the dog y is pressed toward the left byitsspring y in position to engage the arm B when the rheostat-arm hasbeen thrown over to cut out the resistance. To permit the dog y to yieldas the plate 1) passes its tooth 1;, its upper end engages a slot 40* inthe toggle c.

In case it is desired to stop the motor it is only necessary to pressdown the rod 2 to the position shown in Fig. 4, for which purpose a heador button .2 is provided, or the rod might be pulled up to the positionshown in Fig. 5.

With this construction of magnet an adjustment for different loadsordiiferent sizes of motors may be accomplished by raising or loweringthe core J in the solenoid, this being done by loosening its set-nut Jand screwing the core up or down to the desired position andretightening the set-nut.

The double windingql z" for the controlmagnet, which constitutes theprincipal feature of myinvention, (whether applied to the solenoid typeof magnet shown or to any other type of magnet to which it isapplicahle,) has the important advantage that the magnet when acting asan n nde1'loadmagnet is prevented from acting too suddenly or with toogreat sensitiveness. ample,of a mere momentary breakin the main circuit,such as occurs when switching over at the generating-station from onedynamo to another, the magnet will not be instantly demagnetized, andthereby cut out the motor, as has been liable to occur withcontrol-magnets as heretofore made, but, on the contrary, themotor-armature, which is rapidly revolving, continues to revolve becauseof its momentum, and thereby acts for a short time as adynamo-generating current,which traverses the local circuit from onebrush of the motor by way of 31, 30, 29, 28, coil 2', 27, B, 24, 23, and22 back to the other brush of the motor,

so that the current traversing this circuit maintains the excitation ofthe motor-field and also keeps the control-magnet excited until themotor slows down nearly to stopping. lhus even a slow switching over atthe central station, which with prior controlling means would be liableto cut out every motor in the circuit, has no effect when thecontrolmagnets are constructed and connected according to my invention.If the motor-armature races under an accelerating load, its counterelectromotive force,which ordinarily extinguishes the current in theseries coil 2', results in sending a current over the local circuitabove named, which is added to the current from the line through themotor-field winding 30 and shunt-winding 2" of the magnet, so that asthe magnetization of the magnet by the coil 7; decreases it is augmentedin the coil t", and the excitation of the controlmagnet is therebymaintained. If the dynamo should slow down, an effect equivalent to theracing of the motor is produced, and this is compensated for in the samemanner.

As already stated, my generic invention is not limited in itsapplication to a magnet of the solenoid type, but maybe applied to anyform of magnet. For many purposes it is preferable to adopt the form andconstruction of magnet which is set forth and claimed in my aforesaidaprilicatiolnserial No. 723,498, (Patent No. 663,207.) My improvedwinding as applied to this kind of magnet is shown in Figs. 8 and 9. Ineed not here describe the mechanical construction of this magnet, sincethis is fully set forth in my said application. It sutfices to say thatq is the magnet-core, having upper and lower pole-pieces r and r, whichare normally bridged by a movable armature H, pivoted at 93 on a leverI, which is fulcrumed at x and has a retracting spring In the case, forexiOO 25, adjusted by a screw it. In Fig. 9 the armature is shownattracted to the magnet by an overload. In Fig. 8 the armature-lever andretracting means are omitted.

My invention is not limited to any particular arrangement of thewindings z' i. Two modified modes of winding are shown in Figs. 8 and 9.In Fig. 8 the shunt-coil t is wound on the inner part of the spool andthe series coil 1' on the outer part. In Fig. 9 the contrary arrangementis shown, the series coil 2' being wound on the inner part and theshuntcoil L" on the outer part.

My invention is susceptible of other modifications and is not to beunderstood as limited to the precise construction or arrangement ofparts or precise circuit connections shown. Those features which Ibelieve to be essential to my invention are set forth in the claims.

I claim as my invention the following defined novel features,substantially as hereinbetore specified, namely:

1. A magnet for a motor-controller adapted to remain inactive during thenormal range of current variations, and to respond to either a minimumor maximum current, having a double winding comprising a series coil anda shuntcoil wound to receive currents in like direction, so as tocooperate in the magnetization of said magnet, whereby the magnet willnot act as an underload-magnet so long as a magnetizing-currentcontinues in either of said coils.

2. A magnet fora motor-controller adapted to remain inactive during thenormal range of current variations, and to respond to either a minimumor maximum current, having a double winding comprising a series coil anda shunt-coil wound to receive currents in like direction so as tocooperate in the magnetization of said magnet, thev former coil beingconnected in series with the motor-armature and the latter connected inshunt therewith so as to receive a counter-current from the armature.

3. The combination with an electromotor of a control-magnet having twowindings, both wound to receive currents in like direction so as tocooperate in magnetizing it, the one a series coil in series with themotor-armature, and the other a shunt-coil in series with thefield-exciting coil of the motor.

4. The combination with an electromotor of a control-magnet having twowindings, both wound to receive currents in like direction so as tocooperate in magnetizing it, the one a series coil in series with themotor-armature, and the other a shunt-coil in series with thefield-exciting coil of the motor, and a circuit-breaker operated by thedemagnetization of said magnet.

5. The combination with an electromotor of a control-magnet having twowindings, both wound to receive currents in like direction so as tocooperate in magnetizing it, the one a series coil in series with themotor-armature, and the other a shunt-coil in series with thefield-exciting coil of the motor, and a circuitbreaker controlled bysaid magnet and operated to break the circuit between the motor anddynamo when the magnetization of said magnet falls to a minimum or risesto a predetermined maximum.

6. A safety device for an electromotor, comprising a rheostat and itsarm, and an electromagnetic detent for holding said arm in the normalrunning position, adagted to release said arm when its magnetizationfalls to a minimum or rises to a predetermined maximum, said magnethaving a double winding comprising a series coil and a shunt coil woundto receive currents in like direction so as to cooperate in themagnetization of said magnet, whereby a sufficient current in eithercoil will maintain its magnetization.

7. An electromagnetic detent, comprising a catch, a movable memberconnected thereto to withdraw the catch when influenced by a minimum orby a maximum current, and a stationary member magnetically reacting withsaid movable member, and having a series exciting-coil and a sh unt-coilcooperating therewith to magnetize it.

8. An electromagnetic detent comprising a catch, a movable member, astationary member magnetically reacting with said movable.

member, and a connection between said movable member and said catchconsisting of a toggle-link, adapted in an intermediate position of saidmovable member to cause said catch to protrude, and adapted as saidmovable member moves in either direction in response .to an increase ordiminution of magnetism to disengage said catch.

9. An electromagnetic detent comprising stationary and movable membersmagnetically reacting with each other, a catch and a connection betweenthe movable member and said catch, consisting of a pair of toggle-linksarranged to be extended when said movable member is in an intermediateposition, and to be contracted as the movable member moves in eitherdirection in response to an increase or a diminution of magnetism, andconnected to disengage said catch by such contraction.

10. An electromagnetic detent comprising a solenoid having a fixed coiland a movable core, a catch normally protruded, and a pair oftoggle-links connected to said core at their middle part and to saidcatch at one end, whereby when said toggles areshortened by the movementof said core either way from its normal position the catch is withdrawn.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

JAMES J. WOOD.

Witnesses:

A. A. SERVA, T. H. Dasoonn.

